Melatonin is a potent antioxidant that can prevent plant damage caused by adverse stresses. It remains unclear whether exogenous melatonin can mitigate the effects of salt stress on seed germination and seedling growth of sorghum (Sorghum bicolor (L.) Moench). The aim of this study was to decipher the protective mechanisms of exogenous melatonin (100 μmol/L) on sorghum seedlings under NaCl-induced salt stress (120 mmol/L). Plant morphological, photosynthetic, and physiological characteristics were analyzed at different timepoints after sowing. Results showed that salt stress inhibited seed germination, seedling growth, and plant biomass accumulation by reducing photosynthetic pigment contents, photosynthetic efficiency, root vigor, and mineral uptake. In contrast, seed priming with melatonin enhanced photosynthetic pigment biosynthesis, photosynthetic efficiency, root vigor, and K⁺ content under salt stress. Melatonin application additionally enhanced the activities of antioxidant enzymes (superoxide dismutase, catalase, ascorbate peroxidase, and glutathione reductase) and increased the levels of non-enzymatic antioxidants (reduced glutathione, ascorbic acid) in the leaves. These changes were accompanied by increase in the leaf contents of soluble sugars, soluble proteins, and proline, as well as decrease in hydrogen peroxide accumulation, malondialdehyde content, and electrolyte leakage. Our findings indicate that exogenous melatonin can alleviate salt stress-induced damage in sorghum seedlings through multifaceted mechanisms, such as improving photosynthetic performance and root vigor, facilitating ion homeostasis and osmoregulation, and promoting antioxidant defense and reactive oxygen species scavenging.

Justify that the use of selenium has been shown to promote seed germination and seedling growth of some crops under salt stress but the physiological mechanisms in sorghum remain poorly understood. Herein, grain sorghum [Sorghum bicolor (L.) Moench] variety Jinza 2002 was used to explore the effects and mechanisms of seed priming with 25 μmol/L sodium selenite [Se(IV)] on seed germination, seedling growth, antioxidant enzyme activity and osmotic regulatory substances under 120 mmol/L NaCl. The results showed that soaking sorghum seeds in Se(IV) effectively alleviated the harm of salt stress. Compared with the Na group, Se(IV) application increased germination percentage (by 23.8%), while facilitating the elongation of radicles (by 4.2%) and plumules (by 18.4%) under salt stress. Salt-stressed seedlings showed increased levels of leaf chlorophyll, soluble sugar, soluble protein and proline contents, and antioxidant enzyme activities, as well as root activity, and total biomass following Se(IV) application, along with decreased relative electrical conductivity and malondialdehyde content in the leaves. Findings of this study indicate that seed priming with Se(IV) facilitates sorghum seed germination and seedling growth under salt stress by improving root activity, enhancing leaf photosynthesis and antioxidant responses, and reducing cell membrane damage.

The long-term monocropping of red kidney beans in agricultural fields can lead to the occurrence of soil-borne diseases. Alterations in the composition of the soil microbial community are a primary cause of soil-borne diseases and a key factor in continuous cropping obstacles. Research exploring how different cultivation modes can modify the diversity and composition of the rhizosphere microbial community in red kidney beans, and thus mitigate the effects of continuous cropping obstacles, is ongoing. This study employed three cultivation modes: the continuous monocropping of red kidney beans, continuous monocropping of soybeans, and red kidney bean–soybean intercropping. To elucidate the composition and diversity of rhizosphere microbial communities, we conducted amplicon sequencing targeting the V3-V4 hypervariable regions of the bacterial 16S rRNA gene and the ITS1 region of fungal ribosomal DNA across distinct growth stages. The obtained sequencing data provide a robust basis for estimating soil microbial diversity. We observed that, under the intercropping mode, the composition of both bacteria and fungi more closely resembled that of soybean monocropping. The monocropping of red kidney beans increased the richness of rhizosphere bacteria and fungi and promoted the accumulation of pathogenic microorganisms. In contrast, intercropping cultivation and soybean monocropping favored the accumulation of beneficial bacteria such as Bacillus and Streptomyce, reduced pathogenic fungi including Alternaria and Mortierell, and exhibited less microbial variation across different growth stages. Compared to the monocropping of red kidney beans, these systems demonstrated more stable microbial structure and composition. The findings of this study will inform sustainable agricultural practices and soil management strategies.

To identify the key genes conferring resistance to soybean cyst nematode race 4 (SCN4, Heterodera glycines), this study utilized 280 recombinant inbred lines (RILs) derived from the resistant cultivar Huipizhiheidou (HPD) and the susceptible cultivar Jindou23 (JD23). Through phenotypic characterization and a genome-wide association study (GWAS), a genomic region (Gm18:1,223,546–1,782,241) on chromosome 18 was mapped, yielding 14 candidate genes. GmPDH1 was validated as a critical resistance gene using reverse transcription quantitative PCR (RT-qPCR) and Kompetitive Allele Specific PCR (KASP) marker M0526. RT-qPCR revealed that GmPDH1 expression in HPD roots was upregulated 9 days post-inoculation with SCN4 compared to uninoculated controls. KASP genotyping showed that marker M0526 efficiently distinguished between resistant and susceptible plants in natural populations: 71.05% of the resistant accessions exhibited resistant or moderately resistant genotypes, whereas 81.03% of the susceptible accessions showed susceptible or highly susceptible genotypes. Functional validation demonstrated that overexpression of GmPDH1 significantly enhanced SCN4 resistance in the susceptible cultivars JD23 and Jack, whereas CRISPR/Cas9-mediated knockout of GmPDH1 in HPD attenuated its resistance. This study confirmed GmPDH1 as a key gene governing SCN4 resistance and developed an efficient molecular marker, M0526, providing theoretical insights and technical tools for dissecting nematode resistance mechanisms and advancing soybean disease-resistant breeding.

Monoglyceride lipase (MAGL) catalyzes the final step of triacylglycerol (TAG) hydrolysis, converting monoacylglycerol (MAG) into glycerol and free fatty acids. Although MAGL is critical for TAG metabolism, its physiological roles in plants remain poorly understood, compared to its functions in mammals. Eighteen GmMAGL genes were identified from the genome of soybean (Glycine max), a major food and oil crop worldwide, with them being classified into 8 distinct subfamilies. Collinearity analysis indicated that segmental duplication was the only force driving GmMAGL gene family expansion. Multiple sequence alignment demonstrated that all 18 GmMAGLs harbored two typical structural features: the lipase GXSXG (Gly-X-Ser-X-Gly) motif and the catalytic triad consisting of Ser, Asp and His residues. Notably, GmMAGL14 and GmMAGL15 harbored an additional acyltransferase motif, distinguishing them as the only two bifunctional enzymes (hydrolase and acyltransferase) within the GmMAGL family. Additionally, multiple cis-elements associated with development, hormone, and stress response were identified in the promoter regions of GmMAGL genes. RNA-seq data revealed that GmMAGL genes displayed tissue-specific or distinct expression patterns in response to abiotic stresses and hormone treatments. Remarkably, the expression of GmMAGL10 and 14 was negatively related to oil accumulation during seed development while GmMAGL3 exhibited high expressions during seed germination. Particularly, 6 GmMAGL genes (GmMAGL1/3/4/6/8/12) showed significant modulation in response to drought stress in roots and leaves of soybean seedlings. This study represents the first comprehensive identification of 18 members of GmMAGL gene family in soybean. GmMAGL10 and 14 may impact seed oil content negatively while GmMAGL3 function importantly in seed germination. GmMAGL1/3/4/6/8/12 might confer drought tolerance by activating lipid metabolism in soybean seedlings. The present data establish a foundation for further elucidation of the biological functions of GmMAGL genes and provide valuable target genes for genetic improvement in soybean and other crops.